Sci-fi actually needs science

[Ray McCarthy]

Actually even if you are using Fusion power, or even "antimatter" the "rocket equation" still applies. There is a point at which the returns diminish adding more fuel & reaction mass to accelerate for longer. You can't make a spaceship, no matter how big, that accelerates at say 1G half way to a star and then decelerates, using fusion.
Antimatter is really like a "battery". You have to make it, you'd want an automated factory wastefully using fusion power, maybe in orbit at a gas giant. Then if the containment power fails, you loose factory or starship. You won't catch me on an Antimatter powered starship. Turns out you STILL can't accelerate for a few years at 1G etc, the "rocket equation" is the limit.

Real physics is a pain
Tsiolkovsky rocket equation - Wikipedia, the free encyclopedia
(I don't think it covers in space & relativity, but the basic equation is the same)
The sums are a bit tricky, so there is a web site that does them. You can put in what reaction mass you have, power source, efficiency, what power you use to accelerate the reaction mass so you use less (but then you use up hydrogen or antimatter faster, which has to be carried) by throwing it out the back faster, etc, and you can figure how long your ship can accelerate at whatever time period. As you get faster, your rest mass is affected by relativistic factors, so more energy and/or reaction mass is needed to maintain the acceleration.

So don't detail the size, mass, amount of fuel, reaction mass, power source your ship has, unless the plot demands it! Assume only 3 to 6 months acceleration at amounts to give decent healthy gravity effect. If it's really low simulation of gravity, then maybe a couple of years is possible, but the crew / passengers suffer bone loss and organ damage. You can't use more than half the fuel & reaction mass, as you need to decelerate.

EDIT:
Tsiolkovsky and William Moore didn't know about it, the wiki article does explain Relativistic spaceships.
link to here
Relativistic rocket - Wikipedia, the free encyclopedia

The difference between chemical rockets and Solar/Fission/fusion/antimatter is that on a chemical rocket the fuel is also the reaction mass.
Solar needs reaction mass only, but can only work near a star. Xenon is typically used today.
Fission/fusion/antimatter can use fuel waste to add to reaction mass, but usually have a reaction mass too. Water turned to plasma is a likely candidate. For Fusion, some of the hydrogen is used as fuel and waste helium is used as reaction mass also.

In theory you can use light or possibly microwaves, so that you only use fuel and no reaction mass at all. It's not a saving as it might seem as most of the energy is simply wasted. It's more efficient to use your power source to chuck reaction mass out the back.

 

[Ray McCarthy]

The reader doesn't need to be told any of this. But half a day's research will reveal to a writer what is plausible for "conventional" space travel at any star system, excluding the bit of a starship mechanism that somehow gets you between stars, unless you are "coasting" most of the way and only accelerating at start / decelerating at end.

 

[Travis Woodward]

Implausible science has never spoiled my enjoyment of a book. Particularly for distant future sci fi I think many readers don't care about the science really, they're looking for futuristic fantasy.

Factual inaccuracies have spoiled books for me though.

If I read a book with instantaneous teleportation to a planet on the other side of the galaxy it wouldn't bother me. But if they tried to explain it away using, say, quantum entanglement then I'd at least roll my eyes and the immersion would be broken.

The worst example for me is the 'we only use x% of our brain' myth. If a book tries to explain away something using that I almost certainly will give up on it there and then.

 

[Cathbad]

Implausible science has never spoiled my enjoyment of a book. Particularly for distant future sci fi I think many readers don't care about the science really, they're looking for futuristic fantasy.

This may be how you feel (and I'm on your side of the aisle), but I've had too many discussions with sci-fi fans who have felt differently.

'we only use x% of our brain' myth.

No, not what we "use", but what we can "control", which is a very small percentage.

 

[Parson]

@Ray McCarthy nice summary of drive options. That set me thinking about David Weber and his drives. His interstellar drive is a grav wave drive which is a bit like a warp drive. Although it may not be plausible, especially at the speeds Weber imagines, it has to be a bit more "science" than Star Trek warp drives.

Does Star Wars ever try to explain "hyper-speed?"

 

[Cathbad]

@Ray McCarthy nice summary of drive options. That set me thinking about David Weber and his drives. His interstellar drive is a grav wave drive which is a bit like a warp drive. Although it may not be plausible, especially at the speeds Weber imagines, it has to be a bit more "science" than Star Trek warp drives.

Does Star Wars ever try to explain "hyper-speed?"

Yes. It's a bright light that causes you to go fast.

 

[Ray McCarthy]

If I read a book with instantaneous teleportation to a planet on the other side of the galaxy it wouldn't bother me. But if they tried to explain it away using, say, quantum entanglement then I'd at least roll my eyes and the immersion would be broken.

Agree 100% with your post. No difficulty with the Stepping discs in Niven. The ST-TNG explanations of transporter are inherently impossible.

Factual inaccuracies have spoiled books for me though.

All too often these are needless, totally obvious and not important to plot and simply suggest no-one with a non-arts third level ever beta read it and no research was done.

It's easier than ever to research, even if Wikipedia sometimes is wrong or misleading. A few minutes.

Copying stuff on TV or Cinema or "pop culture" because it seems cool is IMO the worst crime and common reason.

 

[Ray McCarthy]

it has to be a bit more "science" than Star Trek warp drives.

All Star Trek needed to do was have it consistent, spend 15 minutes back in 1960s putting rules for the script writers (some brilliant SF writers did novelizations and some scripts of TOS and it recycled quite a few classic SF tropes). Then NEVER tell the viewers how it worked, or have it stupidly inconsistent or the rules. It got sillier and sillier. The idea isn't stupid as such.

Does Star Wars ever try to explain "hyper-speed?"

Not in the original films*. I confess I have watched them many times since seeing 1st Cinema release. I watched two of the next three once. He spoils Star Wars by starting to explain stuff. The wonder and adventure is lost. The rubbish dialogue is separate issue. How the same person can be responsible for Willow (excellent classic) and Phantom Menace is a mystery to me.
A lot of Star Wars is inspired by Dune.
[* There the famous Kessel run verbal mistake. Fans make too much of this. People in real life make similar errors all the time. That doesn't bother me at all. See I'm not as pedantic as you think!]

 

[StilLearning]

Actually even if you are using Fusion power, or even "antimatter" the "rocket equation" still applies...

Sorry for my pedantry here, but you mentioned using light or microwaves; There is a class of microwave/light using spaceship engines that can circumvent the rocket equation, known as lightsails: The fuel, and the reactor, stays on earth or near Earth. The power they produce is transmitted out to the ship using a laser, microwave or other means of transmission. The ship can simply ride the beam using a reflective sail (thanks to a phenomena known as radiation pressure), or make use of it in some other way. The sail side of things has been tested and flown in space, using sunlight, by the Japanese IKAROS spaceship, but to get a vehicle up to any sort of interstellar speed would need a powerful array of lasers shining on the sail (although a very, very close pass of the Sun's surface will also work if you can do that without cooking your ship).

You still waste a lot of energy, but not nearly as much as you would lugging all your fuel up to interstellar speeds with you. Lightsails are being seriously proposed as a technology that would let us launched a small unmanned probe to a nearby star in the next 50 years, by a project called the breakthrough starshot initiative. They're widely thought to be the most realistic interstellar drive proposed, barring something game changing in fundamental physics (like if the Cannae drive turns our to be what it's claimed to be). Their downside is they very much work best for tiny, lightweight, unmanned probes - vehicles about as far from the starship enterprise as you can get. In fact the idea is often referred to as a 'starwisp' rather than a starship.

 

[Ray McCarthy]

There is a class of microwave/light using spaceship engines that can circumvent the rocket equation, known as lightsails: The fuel, and the reactor, stays on earth or near Earth. The power they produce is transmitted out to the ship using a laser, microwave or other means of transmission.

I didn't mention that as it's not practical for Interstellar use. Though there is a Crazy Eddie "Motie" craft in Larry Niven (Mote in God's Eye?) that does do it for Interstellar travel.
It has serious limitations even in a star system. However, despite that, there is work ongoing as the mass to put in orbit to perhaps send probe to asteroids or Jupiter's moons is much reduced. It's not a viable manned Interstellar craft.

The "starshot" initiative only gives acceleration to leave the solar system, which we have achieved five times I think. It's extremely limited in scope and the craft would be very small and take lifetimes to get anywhere.
In the context of Science in SF with star travel it's hard to swallow and was the worst bit in the Niven book. I had an immediate reaction of this is like Piers Anthony's Xanth, not serious. Even the power of a star isn't enough!

 

[Mirannan]

Two points I'd like to make:

First is that the laser-powered lightsail has a non-physical and even non-engineering problem. It's simply this: Who do you trust with the multi-petawatt laser battery that it needs to work?

The second is that the Kessel run gaffe might not actually be a gaffe. It depends on the way your hyperdrive works, but if it works by finding higher-dimensional shortcuts through spacetime then there might be a choice of routes - good pilots finding the shorter routes.

 

[SilentRoamer]

The second is that the Kessel run gaffe might not actually be a gaffe. It depends on the way your hyperdrive works, but if it works by finding higher-dimensional shortcuts through spacetime then there might be a choice of routes - good pilots finding the shorter routes.

I always thought this was the case.

As I understood it the Kessel run traversed close to the Maw (I think) which was a very dangerous area of space near a black hole. So to cover the Kessel run in a shorter distance requires a powerful navigational system. The upgrades to the Millenium Falcon included one of the best navigational systems meaning the MF could make the journey in a shorter distance.

 

[Vertigo]

Another problem with the light sail option, even if you could get up to sensible speeds and if you could trust someone to keep firing a laser at you for the probably at least centuries (if not millennia) involved, is how do you slow down? Unless there's someone at the other end to direct a laser at you then you're a bit stuffed. Bit of a chicken and egg problem.

Realistically it's never going to be any use over interstellar distances; acceleration is going to be so low you are realistically talking about thousands of years for the shortest of interstellar journeys.

 

[Ray McCarthy]

The second is that the Kessel run gaffe might not actually be a gaffe.

Least worrying aspect of the entire franchise

Who do you trust with the multi-petawatt laser battery that it needs to work?

I wonder is US DOD funding any of the research?

 

[J D Foster]

Beyond a certain level of scientific / mathematical / engineering education, having POINTLESS violations of logic, science, maths etc is just plain very annoying. It most times is on the level of having Elizabeth I before Henry VIII, or a US city in wrong State, a plain lack of research.

It honestly doesn't bother me at all. Since I don't understand a drop of physics I wouldn't mind (or care) if a story broke the rules I don't know or understand.

 

[J Riff]

Physics is pain. Refer to: the Inverted Squared Circle theory. Mass is equal to weight + fat molecules. In space, no-one can hear me theorize. Thought is faster than light, even in this neighborhood. Birds fly, yet don't know physics, so that proves that living spaceships might not be able to explain how they do it, either.

 

[Parson]

Though there is a Crazy Eddie "Motie" craft in Larry Niven (Mote in God's Eye?) that does do it for Interstellar travel.

Indeed, "Mote in God's Eye," one of S.F.'s all time classics. But I'm not sure if it was truly interstellar. The Moties had developed what they called "The Crazy Eddie Drive" because it made ships disappear. The problem was that interstellar flight was made by a series of jumps to jump points, which were where they were without relation to any discernible rhyme or reason. The one jump point out of the Motie home was right into a star's corona. Human ships could survive because they had shields and it was the one piece of technology the Moties had not developed. It was a nearby star and might even have been a binary system at least that's what I thought. The mote propulsion beam (understand lasar beam) had been firing for 100 years so I suspect that we are not talking about multiple light year distances.

 

[Ray McCarthy]

"The Crazy Eddie Drive" because it made ships disappear.

Yes I was mixing up two things. On the gripping hand, the light propelled ship seems to have been at a different system when intercepted? I've only read that one once. Great series, I thought there were three books, but one has two titles, though perhaps there is a third book?
Anyway, I have two books with the moties and great fun.
Another eyebrow raiser is a system with two planets on the same orbit. Not impossible, (each others
Lagrange points?) but highly improbable and not long term stable, unless I misread it.

I've not yet managed to get any of his Fantasy titles. Looking forward to trying some.

 

[Parson]

I'm going to have to look at that. I believe I've only read "The Mote in God's Eye." If that is so, I have some entertaining reading to get done.

 

[StilLearning]

I didn't mention that as it's not practical for Interstellar use. Though there is a Crazy Eddie "Motie" craft in Larry Niven (Mote in God's Eye?) that does do it for Interstellar travel.
It has serious limitations even in a star system. However, despite that, there is work ongoing as the mass to put in orbit to perhaps send probe to asteroids or Jupiter's moons is much reduced. It's not a viable manned Interstellar craft.

The "starshot" initiative only gives acceleration to leave the solar system, which we have achieved five times I think. It's extremely limited in scope and the craft would be very small and take lifetimes to get anywhere.
In the context of Science in SF with star travel it's hard to swallow and was the worst bit in the Niven book. I had an immediate reaction of this is like Piers Anthony's Xanth, not serious. Even the power of a star isn't enough!

Ahem, sorry, pedantic here again: It's true that other craft are leaving the solar system. Vehicles like New Horizons are doing speeds in the region of tens of kilometers per second. The starshot initiative's stated goal is to demonstarte the feasiblity of sendng a probe to another star within a human lifetime, which needs speeds of 15,000 km/sec minimum, even asumng you get a 80 year lifespan. It's a very different kettle of babel fish.